title: Interpretation of food specific immunoglobulin E levels in the context of total IgE.
abstract: BACKGROUND
  Food specific immunoglobulin E (IgE) (fsIgE) cut points are used in the evaluation of food allergies. Concomitant measurement of total IgE (tIgE) is traditionally not obtained. We anecdotally observed elevations in fsIgE mirroring tIgE increases, which may confound accurate interpretation.
  
  
  OBJECTIVE
  To determine whether changes in tIgE were associated with fsIgE and whether predictions of fsIgE could be formulated based on tIgE.
  
  
  METHODS
  We studied children younger than 18 years who had both tIgE and fsIgE (egg, n = 136; milk, n = 123; peanut, n = 201; soy, n = 55) obtained simultaneously on 1 or more occasion between January 2008 and February 2011. After institutional review board approval, natural log-transformed (ln) tIgE and fsIgE levels were analyzed using univariate and multivariate regression models to assess associations and predict fsIgE using tIgE and other covariates.
  
  
  RESULTS
  Soy IgE levels were strongly correlated (ρ = 0.85, P < .001), whereas egg, milk, and peanut IgE levels were substantially correlated (ρ = 0.69, 0.69, and 0.66, respectively, P < .001) with tIgE. A 1-unit increase in ln(tIgE) was significantly correlated with unit increases in ln(egg IgE) (0.77), ln(milk IgE) (0.84), ln(peanut IgE) (0.87), and ln(soy IgE) (0.89) (P < .001). The ln(tIgE)-based univariate models could predict fsIgE in the validation data with strong (soy) and substantial (egg, milk, and peanut) predictive ability (P < .001).
  
  
  CONCLUSIONS
  Our study found significant and parallel relationships between tIgE and fsIgE levels to egg, milk, peanut, and soy. It underscores the importance of examining fsIgE levels in context of tIgE while making diagnostic and management decisions in children with food allergies.
authors.affiliation: Children's Mercy Hospitals and Clinics, Kansas City, Missouri 64108, USA.
authors.forename: Tara J
authors.initials: TJ
authors.lastname: Federly
authors.forename: Bridgette L
authors.initials: BL
authors.lastname: Jones
authors.forename: Hongying
authors.initials: H
authors.lastname: Dai
authors.forename: Chitra
authors.initials: C
authors.lastname: Dinakar
mesh_terms: D000485:Allergens / Q000276:immunology; D000818:Animals; D002675:Child, Preschool; D021181:Egg Hypersensitivity / Q000276:immunology; D005260:Female; D005512:Food Hypersensitivity / Q000276:immunology*; D006801:Humans; D007073:Immunoglobulin E / Q000097:blood*; D008297:Male; D008892:Milk / Q000276:immunology; D016269:Milk Hypersensitivity / Q000276:immunology; D010063:Ovum / Q000276:immunology; D021183:Peanut Hypersensitivity / Q000276:immunology; D012882:Skin Tests; D045730:Soy Foods; D013025:Glycine max / Q000276:immunology
chemical_list: D000485:Allergens; D007073:Immunoglobulin E